Tunable dual-band band-pass filter

ABSTRACT

A tunable dual-band resonator and a tunable dual-band band-pass filter using the tunable dual-band resonator. The dual-band resonator is structured such that a stub is added to each half-wavelength resonator provided with half-wavelength resonator protrusions (capacity-component adjust parts). The dual-band resonator is made up of an odd-number mode resonator in a shape including a ground conductor disposed on the back surface of a dielectric body, and a strip conductor disposed on the top surface thereof, and an even-number mode resonator in such a shape as to be formed when the stub is connected to an end face on the opposite side of the open-end of the strip, characterized in that a dielectric rod having a circular cross section is provided in the space above the respective stubs and another dielectric rod having a circular cross section is provided in the space above the half-wavelength resonator protrusions.

This application is a divisional of prior U.S. application Ser. No.14/808 183, filed Jul. 24, 2015, which is hereby incorporated byreference in its entirety.

The invention relates to frequency-tuning as well as improvement(trimming) of the band-pass characteristics of equipment using ahigh-frequency wave and a microwave, that is, a tunable dual-bandband-pass filter utilized for transmitting/receiving of a signal, in thefield of communication technology, including, for example, mobilecommunication, satellite communication, fixed microwave communication,etc.

BACKGROUND OF THE INVENTION

Data communications for video, and so forth have recently undergone atremendous explosion in use, so that network-capacity crunch andfrequency-resources crunch are anticipated on a worldwide basis, posinga major problem. In order to cope with this situation, development of amicrowave filter for use by a base station of mobile communications isasked for so as to concurrently implement the effective utilization ofhigh-speed/large-capacity communication and frequency-resources.Further, communication equipment capable of coping with a plurality offrequency-bands is also lately desired.

A method of communication by the concurrent use of two frequency-bandshas been proposed as one of the methods for implementinghigh-speed/large-capacity communication. There has been proposed adual-band band-pass filter which allows two frequency-bands toconcurrently pass therethrough, representing the elemental technology ofthe method described as above.

There exists the traditional method of making up a dual-band band-passfilter having two pass-bands, as described hereunder. As shown in FIG.1, a plurality of a dual-band resonators N1, N2, and N3, resonating attwo frequencies, are subserviently coupled with each other, to becoupled with input/output ports Ml, M2, provided at the respective endsof subservient coupling, thereby making up a filter 100 (Non-patentDocument 1).

The dual-band resonators N1, N2, N3 each has even-number/odd-numbermodes, and the dual-band band-pass filter having the two pass-bands ismade up by controlling these two modes. With this filter 100, there isthe need for directly coupling the input/output ports M1, M2 to thedual-band resonators N1, and N3, at the respective ends of the filter100, thereby deciding a connection position for enabling desiredcharacteristics to be concurrently obtained in both the two pass-bands.

Meanwhile, a band-pass filter having an abrupt cut-off characteristic isrequired for effective utilization of frequency-resources. In general,an abrupt cut-off characteristic can be realized by adoption of amultistage operation to thereby increase the number of resonators.However, since a normal conductor, such as copper, etc., has aresistance, an insertion loss will increase along with the multistageoperation, so that it has been impossible to realize a trade-off betweena low-loss and the abrupt cut-off characteristic. There has beenproposed, for example, a superconducting band-pass filter, as one of themethods for solving this problem (Patent document 1). As asuperconductor has a surface resistance lower by 2 to 3 orders ofmagnitude as compared with copper, etc., in a microwave-band, so thatthe insertion loss can be suppressed to be low even after a multistageoperation, thereby enabling the trade-off between the low-loss and theabrupt cut-off characteristic to be realized.

Further, there has been proposed a center-frequency tunable dual-bandband-pass filter capable of varying the center-frequency of theband-pass filter, as a method coping with a plurality offrequency-bands.

FIG. 2 of Patent document 2 is a view showing the configuration of atraditional superconducting tunable dual-band band-pass filter by way ofexample. A dielectric plate S10 is disposed above a microstrip-typefilter pattern S1 formed on a dielectric substrate S5. A distance hbetween the dielectric plate S10 and the filter pattern S1 is varied byuse of an actuator such as a piezoelectric element, etc. and so forth,to cause an electric-field distribution radiated from the filter patternS1 to be varied, thereby rendering the center-frequency variable (Patentdocument 2).

A dual-band band-pass filter is realized by use of a dual-band resonatorcapable of realizing a resonance frequency in two pass-bands by use ofone resonator. A center-frequency, in the respective bands of thedual-band band-pass filter shown in FIG. 1, is dependent on theeven-number/odd-number modes occurring to the respective dual-bandresonators N1, N2, and N3. Because the respective odd-number modeportions of the dual-band resonators N1, N2, N3 are for use in commonwith the even-number modes, adjustment of the odd-number modes affectsthe even-number modes. A bandwidth of each band is controlled by adistance between the resonators with respect to the respective dual-bandresonators N1, N2, N3, however, if the tuning of the center-frequency isapplied to this dual-band band-pass filter by use of the dielectricplate S10, this will cause the whole surface above the dual-bandband-pass filter to be covered with the dielectric plate. Accordingly,both modes of the even-number/odd-number modes of the dual-bandband-pass filter will be affected, so that the tuning of thecenter-frequency is possible, however, it is difficult to tune thecenter-frequency independently of the even-number/odd-number modes.Further, since the filter in whole is covered with the dielectric plate,an electromagnetic field distribution between the dual-band resonators,as well, will be affected, thereby causing a problem in that thebandwidth as well undergoes variation. Furthermore, an increase in theshift amount of the center-frequency will result in degeneration of theband-pass characteristics, so that a trimming mechanism for adjustmentof the resonance frequency of each of the resonators will be requiredaside from a frequency tuning mechanism. Herein, by “trimming” is meanta method of improvement of the band-pass characteristics.

The inventors have proposed a center-frequency tunable dual-bandband-pass filter, as a method of solving these problems, as shown inPatent Document 3. The center-frequency tunable dual-band band-passfilter is capable of tuning (varying) two pass-bands independently ofrespective center-frequencies, and improving the band-passcharacteristics that will degenerate after the tuning of the respectivecenter-frequencies by use of the frequency tuning mechanism withoutnewly introducing the trimming mechanism.

Further, in FIG. 3, mention is made of a dielectric rod 25 that has anellipse-like cross section and is highly efficient in varying a shiftamount of resonance in the odd-number mode, thereby proposing that theshift amount of the resonance in the odd-number mode can be changed byinstalling the dielectric rod 25, in a space above a half-wavelengthresonator 10. However, upon fine-tuning of the space between thehalf-wavelength resonator 10 and the dielectric rod 25, if the crosssection of the dielectric rod 25 is ellipse-like in shape, a tip portionof the long diameter of the ellipse will exceed the width of the stripconductor of the half-wavelength resonator 10 when rotated, therebycausing a characteristic in value to be extremely changed, so that thereis the need for causing the dielectric rod 25 to approach thehalf-wavelength resonator 10, or to distance itself from thehalf-wavelength resonator 10. Accordingly, upon the fine-tuning of thespace between the half-wavelength resonator 10 and the dielectric rod25, a special device is required of the dielectric rod 25 having anellipse-like cross section.

In the case of a dual-band band-pass filter using a superconductor, inparticular, a measurement is conducted in a vacuum chamber, whilecooling to −200° C. or lower by use of a refrigerator, and there istherefore the need for raising or lowering the dielectric rod 25 byvertically moving it from outside the chamber. For this reason, it isparticularly desirous for the dielectric rod 25 to be structured so asto be pushed in by turning a screw. In such a case, if the rod 25 isformed in the shape of an ellipse in order to increase the shift amountof the resonance in the odd-number mode, there will arise the need for amechanism capable of raising and lowering the rod 25 without rotatingthe same, whereupon the tuning mechanism will be considerablycomplicated to thereby cause an increase in size. In this case, there isa possibility that the tuning mechanism itself cannot be installed abovethe filter, thereby posing a problem in that use of the rod 25 in theshape of the ellipse is not practical from the viewpoint of cost.

PRIOR ART DOCUMENTS

Patent Document 1: JP 2002-57506A

Patent Document 2: JP 3535469B2

Patent Document 3: JP 2014-014962

Non-Patent Document: Jia-Sheng Hong, Wenxing Tang, “Dual-band filterbased on non-degenerate dual-mode slow-wave open-loop resonators”, IEEEMTT-S International Microwave Symposium Digest, pp. 861-864, 2009.

SUMMARY OF THE INVENTION

The present invention proposed is a dual-band band-pass filter efficientin varying the shift amount of resonance in an odd-number mode withoutrequiring a special device.

A representative dual-band resonator for use in the present invention isof a basic structure in which a stub 11 is added to a half-wavelengthresonator 10 provided with half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b as shown in FIG. 4.

As to the shape of each of the half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b, it need only be sufficientfor the half-wavelength resonator protrusion to protrude along a stripconductor, and it may be rectangular or staircase-like in shape,however, preferably laterally symmetric in shape. The half-wavelengthresonator protrusions (capacity-component adjust parts) 10-a, 10-b arebasically conductors capable of conducting electricity excellently likethe strip conductor.

As shown in FIG. 4, with the dual-band resonator structured such thatthe stub 11 is added to each half-wavelength resonator 10, symmetric A-Bplanes of the stubs 11 function as an electrical/magnetic wall,respectively. The dual-band resonator operates in two frequency-bandsdue to the resonance in an odd-number mode and resonance in aneven-number mode, and can adjust a resonator length such that thehalf-wavelength resonator 10 serves as the resonator in the odd-numbermode and the half-wavelength resonator 10 and the stub serve 11 as theresonator in the even-number mode, thereby causing the odd-number modeto resonate on a low-frequency side, while causing the even-number modeto resonate on a high-frequency side, alternatively enabling theodd-number mode to resonate on the high-frequency side, while enablingthe even-number mode to resonate on the low-frequency side.

The dual-band resonator is made up of an odd-number mode resonatorincluding a ground conductor in a predetermined thickness disposed onthe back surface of a dielectric body, and a strip conductor disposed onthe top surface thereof, wherein the relevant strip conductor is onelength of a thin strip conductor cut off at an open-end thereof (thelocation where the strip is not linked), provided with a deeplyretreated groove having a width g, one length of the strip conductor isin a laterally symmetric shape, having a width d, and provided at thetip of the groove as well as the end face of the strip conductor, and aneven-number mode resonator in such a shape that the stub 11 having alength 1 is connected to an end face on the opposite side of theopen-end of the strip. The dual-band resonator operates as theodd-number mode resonator, when the electric current flows to thesymmetric A-B planes of the stubs 11, while operating as the even-numbermode resonator when the electric current does not flow to the symmetricA-B planes, as shown in FIG. 5. The inventors of the present inventionfound a structure enabling the dual-band resonator to be tunable, whichwas as disclosed in Patent Document 3. With the tunable dual-bandresonator according to the present invention, the frequencycharacteristics in the odd-number mode was further improved.

That is, the present invention provides a tunable dual-band resonatorstructured such that a stub is added to each half-wavelength resonator10, and each thereof is provided with half-wavelength resonatorprotrusions (capacity-component adjust parts) 10-a, 10-b, and symmetricA-B planes of the stubs 11, functioning as an electrical/magnetic wall,respectively.

The dual-band resonator operates in two frequency-bands due to theresonance in an odd-number mode and resonance in an even-number mode(resonance), and can adjust a resonator length such that thehalf-wavelength resonator 10 serves as the resonator in the odd-numbermode, while the half-wavelength resonator 10 and the stub 11 serve asthe resonator in the even-number mode, thereby causing the odd-numbermode to resonate on a low-frequency side, while causing the even-numbermode to resonate on a high-frequency side, alternatively, enabling theodd-number mode to resonate on the high-frequency side, while enablingthe even-number mode to resonate on the low-frequency side.

The dual-band resonator is made up of an odd-number mode resonator inthe shape including a ground conductor in a predetermined thicknessdisposed on the back surface of a dielectric body, and a strip conductordisposed on the top surface of the dielectric body, the relevant stripconductor is one length of a thin strip conductor cut off at an open-endthereof (the location where the strip is not linked), provided with adeeply retreated groove having a width g, and one length of the stripconductor is in a laterally symmetric shape, having a width d, andprovided at the tip of the groove as well as the end face of the stripconductor, and an even-number mode resonator in such a shape as to beformed when the stub 11 having a length 1 is connected to an end face onthe opposite side of the open-end of the strip, wherein the dual-bandresonator operates as the odd-number mode resonator, when the electriccurrent flows to the symmetric A-B planes of the stubs 11, whileoperating as the even-number mode resonator when the electric currentdoes not flow to the symmetric A-B planes, characterized in that adielectric rod 25 having a circular cross section is provided in thespace above the respective stubs 11, a dielectric rod 25 having acircular cross section is provided in the space above thehalf-wavelength resonator protrusions (capacity-component adjust parts)10-a, 10-b of the half-wavelength resonator 10, enabling a resonancefrequency in the even-number mode, and a resonance frequency in theodd-number mode to be tuned independently from each other.

Still further, the present invention provides a tunable dual-bandband-pass filter having a structure incorporating a dual-band structuredsuch that a stub is added to each half-wavelength resonator 10, eachthereof being provided with half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b, and symmetric A-B planesof the stubs 11 functioning as an electrical/magnetic wall,respectively.

The dual-band resonator operates in two frequency-bands due to theresonance in an odd-number mode and resonance in an even-number mode,and can adjust a resonator length such that the half-wavelengthresonator 10 serves as the resonator in the odd-number mode, while thehalf-wavelength resonator 10 and the stub 11 serve as the resonator inthe even-number mode, thereby causing the odd-number mode to resonate ona low-frequency side, while causing the even-number mode to resonate ona high-frequency side, alternatively, enabling the odd-number mode toresonate on the high-frequency side, while enabling the even-number modeto resonate on the low-frequency side.

The dual-band resonator is made up of an odd-number mode resonator in ashape including a ground conductor in a predetermined thickness disposedon the back surface of a dielectric body, and a strip conductor disposedon the top surface of the dielectric body, the relevant strip conductoris one length of a thin strip conductor cut off at the open-end thereof(the location where the strip is not linked), and provided with a deeplyretreated groove having a width g, and one length of the strip conductoris in a laterally symmetric shape, having a width d, and provided at thetip of the groove as well as the end face of the strip conductor, andincluding the half-wavelength resonator protrusions (capacity-componentadjust parts) 10-a, 10-b, and an even-number mode resonator in such ashape as to be formed when the stub 11 having a length 1 is connected toan end face on the opposite side of the open-end of the strip, whereinthe dual band resonator operates as the odd-number mode resonator whenthe electric current flows to the symmetric A-B planes of the stubs 11,while operating as the even-number mode resonator when the electriccurrent does not flow to the symmetric A-B planes, characterized in thata dielectric rod 25 having a circular cross section is provided in thespace above the half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b of the half-wavelengthresonator 10 and a dielectric rod 25 having a circular cross section isprovided in the space above the respective stubs 11.

Further, the present invention provides a multistage-type (two-stage)dual-band band-pass filter having a structure incorporating three units(in total) of dual-band resonators (first and second resonators), andeach dual-band resonator is structured such that a stub 11 is added toeach half-wavelength resonator 10, and each thereof is provided withhalf-wavelength resonator protrusions (capacity-component adjust parts)10-a, 10-b, and symmetric A-B planes of the stubs 11 function as anelectrical/magnetic wall, respectively.

The dual-band resonator operates in two frequency-bands due to resonancein an odd-number mode and resonance in an even-number mode, and canadjust a resonator length such that the half-wavelength resonator 10serves as the resonator in the odd-number mode, whereas thehalf-wavelength resonator 10 and the stub 11 serve as the resonator inthe even-number mode, thereby causing the odd-number mode to resonate ona low-frequency side, while causing the even-number mode to resonate ona high-frequency side, alternatively, enabling the odd-number mode toresonate on the high-frequency side, while enabling the even-number modeto resonate on the low-frequency side.

The first dual-band resonator is made up of an odd-number mode resonatorin a shape including a ground conductor in a predetermined thicknessdisposed on the back surface of a dielectric body, and a strip conductordisposed on the top surface of the dielectric body, the relevant stripconductor is one length of a thin strip conductor cut off at theopen-end thereof (the location where the strip is not linked), andprovided with a deeply retreated groove having a width g, and one lengthof the strip conductor is in a laterally symmetric shape, having a widthd, and provided at the tip of the groove as well as the end face of thestrip conductor, and also including the half-wavelength resonatorprotrusions (capacity-component adjust parts) 10-a, 10-b, and aneven-number mode resonator in such a shape as to be formed when the stub11 having a length 1 is connected to an end face on the opposite side ofthe open-end of the strip, wherein the dual band resonator operates asthe odd-number mode resonator when the electric current flows to thesymmetric A-B planes of the stubs 11, while operating as the even-numbermode resonator when the electric current does not flow to the symmetricA-B planes. The second dual-band resonator is identical in configurationto the first dual-band resonator, and the orientation thereof is variedby 180 degrees, provided with an H-shaped waveguide 12, an end facethereof having a length n, and located at a given interval m away fromthe first dual-band resonator, wherein feeder conductor lines 13 areprovided along half-wavelength resonator 10 of the first dual-bandresonator as well as the second dual-band resonator, and wherein thefeeder conductor line 13 on one side, functions as an input side, whilethe feeder conductor line 13 on the other side, functions as an outputside, characterized in that a dielectric rod 25 having a circular crosssection is provided in the space above each of the half-wavelengthresonator protrusions (capacity-component adjust parts) 10-a, 10-b ofthe half-wavelength resonator 10, and a dielectric rod 25 having acircular cross section is provided in the space above each of therespective stubs 11.

Furthermore, with the two-stage dual-band band-pass filter according tothe present invention, there is provided a method of adjusting the shiftamount of frequency-tuning so as to adjust the band-pass characteristicsin the odd-number mode alone by adjusting the distance of only therespective dielectric rods 25 having a circular cross section, providedin the space above the half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b of the half-wavelengthresonator 10, from the tunable dual-band band-pass filter, entirely atthe same height.

Still further, with the two-stage dual-band band-pass filter accordingto the present invention, there is provided a method of adjusting toshift amount of frequency-tuning so as to adjust the band-passcharacteristics in the even-number mode alone by adjusting the distancesof only the respective rods 25 having a circular cross section, providedin the space above the respective stubs 11, from the tunable dual-bandband-pass filter, entirely at the same height.

Still furthermore, with reference to the adjustment method according tothe present invention, in the method of improving (trimming) thedegeneration in the band-pass characteristics, occurring after thetuning of the respective center-frequencies in the two-stage tunabledual-band band-pass filter, the band-pass characteristics in the oddnumber mode alone can be improved by individually adjusting the distanceof only the respective dielectric rod 25 having a circular crosssection, provided in the space above the half-wavelength resonatorprotrusions (capacity-component adjust parts) 10-a, 10-b of thehalf-wavelength resonator 10, from the tunable dual-band band-passfilter.

Yet further, with reference to the adjustment method according to thepresent invention, in the method of improving (trimming) thedegeneration in the band-pass characteristics, occurring after thetuning of the respective center-frequencies in the two-stage tunabledual-band band-pass filter, the band-pass characteristics in theeven-number mode alone can be improved by individually adjusting thedistance of only the respective dielectric rod 25 having a circularcross section, provided in the space above the respective stubs 11, fromthe tunable dual-band band-pass filter.

Further, the present invention provides a multistage-type (three-stage)dual-band band-pass filter having a structure incorporating three-units(in total) of dual-band resonators (first, second and third resonators),and each dual-band resonator is structured such that a stub 11 is addedto each half-wavelength resonator 10, and provided with half-wavelengthresonator protrusions (capacity-component adjust parts) 10-a, 10-b, andsymmetric A-B planes of the stubs 11 function as an electrical/magneticwall, respectively.

The dual-band resonator operates in two frequency-bands due to theresonance in an odd-number mode and resonance in an even-number mode,and can adjust the resonator length such that the half-wavelengthresonator 10 serves as the resonator in the odd-number mode, whereas thehalf-wavelength resonator 10 and the stub 11 serve as the resonator inthe even-number mode, thereby causing the odd-number mode to resonate ona low-frequency side, while causing the even-number mode to resonate ona high-frequency side, alternatively, enabling the odd-number mode toresonate on the high-frequency side, while enabling the even-number modeto resonate on the low-frequency side.

The first dual-band resonator is made up of an odd-number moderesonance-waveguide in a shape including a ground conductor in apredetermined thickness disposed on the back surface of a dielectricbody, and a strip conductor disposed on the top surface of thedielectric body, and the relevant strip conductor is one length of athin strip conductor cut off at the open-end thereof (the location wherethe strip is not linked), and provided with a deeply retreated groovehaving a width g, and one length of the strip conductor is in alaterally symmetric shape, having a width d, and provided at the tip ofthe groove as well as the end face of the strip conductor, and alsoincluding the half-wavelength resonator protrusions (capacity-componentadjust parts) 10-a, 10-b, and an even-number mode resonance-waveguide insuch a shape as to be formed when the stub 11 having a length 1 isconnected to an end face on the opposite side of the open-end of thestrip, wherein the first dual band resonator operates as the odd-numbermode resonance-waveguide, when the electric current flows to thesymmetric A-B planes of the stubs 11, while operating as the even-numbermode resonance-waveguide when the electric current does not flow to thesymmetric A-B planes. The second dual-band resonator is identical inconfiguration to the first dual-band resonator, and the orientationthereof is varied by 180 degrees, and provided with an H-shapedwaveguide 12, an end face thereof having a length n, and located at agiven interval m away from the first dual-band resonator, andincorporates the half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b. The third dual-bandresonator is identical in configuration to the first dual-bandresonator, and the orientation thereof is varied by 180 degrees, andprovided with an H-shaped waveguide 12, an end face thereof having alength n, and located at a given interval m away from the seconddual-band resonator. The second dual-band resonator is provided betweenthe first dual-band resonator and the third dual-band resonator, whereinfeeder conductor lines 13 are provided along the half-wavelengthresonator 10 of the first dual-band resonator as well as the thirddual-band resonator, the feeder conductor line 13 on one side functionsas an input side, while the feeder conductor line 13 on the other sidefunctions as an output side. Whereupon the multistage-type dual-bandband-pass filter serves as the three-stage dual-band band-pass filter,characterized in that a dielectric rod 25 having a circular crosssection is provided in the space above each of the half-wavelengthresonator protrusions (capacity-component adjust parts) 10-a, 10-b ofthe half-wavelength resonator 10, and the dielectric rod 25 having acircular cross section is provided in the space above each of therespective stubs 11.

Furthermore, with the three-stage dual-band band-pass filter accordingto the present invention, there is provided a method of adjusting theshift amount of frequency-tuning so as to adjust the band-passcharacteristics in the odd-number mode alone by adjusting the distanceof only the respective dielectric rods 25 having a circular crosssection, provided in the space above the half-wavelength resonatorprotrusions (capacity-component adjust parts) 10-a, 10-b of thehalf-wavelength resonator 10, from the tunable dual-band band-passfilter.

Still further, with the three-stage dual-band band-pass filter accordingto the present invention, there is provided a method of adjusting theshift amount of frequency-tuning so as to adjust the band-passcharacteristics in the even-number mode alone by adjusting the distancesof only the respective rods 25 having a circular cross section, providedin the space above the respective stubs 11, from the tunable dual-bandband-pass filter.

Still furthermore, with reference to the adjustment method according tothe present invention, in the method of improving (trimming) thedegeneration in the band-pass characteristics, occurring after thetuning of the respective center-frequencies in the three-stage tunabledual-band band-pass filter, the band-pass characteristics in theodd-number mode alone can be improved by individually adjusting thedistance of only the respective dielectric rod 25 having a circularcross section, provided in the space above the half-wavelength resonatorprotrusions (capacity-component adjust parts) 10-a, 10-b of thehalf-wavelength resonator 10, from the tunable dual-band band-passfilter.

Yet further, with reference to the adjustment method according to thepresent invention, in the method of improving (trimming) thedegeneration in the band-pass characteristics, occurring after thetuning of the respective center-frequencies in the three-stage tunabledual-band band-pass filter, the band-pass characteristics in theeven-number mode alone can be improved by individually adjusting thedistance of only the respective dielectric rod 25 having a circularcross section, provided in the space above the respective stubs 11, fromthe tunable dual-band band-pass filter.

Further, the present invention provides a multistage-type (n-stage)dual-band band-pass filter having a structure incorporating n-units (intotal) of dual-band resonators (first, second, third, fourth, . . . nthresonators), and each dual-band resonator is structured such that a stub11 is added to each half-wavelength resonators 10, and provided withhalf-wavelength resonator protrusions (capacity-component adjust parts)10-a, 10-b, and symmetric A-B planes of the stubs 11 function as anelectrical/magnetic wall, respectively.

The dual-band resonator operates in two frequency-bands due to theresonance in an odd-number mode and resonance in an even-number mode,and can adjust the resonator length such that the half-wavelengthresonator 10 serves as the resonator in the odd-number mode, whereas thehalf-wavelength resonator 10 and the stub 11 serve as the resonator inthe even-number mode, thereby causing the odd-number mode to resonate ona low-frequency side, while causing the even-number mode to resonate ona high-frequency side, alternatively, enabling the odd-number mode toresonate on the high-frequency side, while enabling the even-number modeto resonate on the low-frequency side.

The first dual-band resonator is made up of an odd-number moderesonance-waveguide in a shape including a ground conductor in apredetermined thickness disposed on the back surface of a dielectricbody, and a strip conductor disposed on the top surface of thedielectric body, and the relevant strip conductor is one length of athin strip conductor cut off at the open-end thereof (the location wherethe strip is not linked), and provided with a deeply retreated groovehaving a width g, and one length of the strip conductor is in alaterally symmetric shape, having a width d, and provided at the tip ofthe groove as well as the end face of the strip conductor, and alsoincluding the half-wavelength resonator protrusions (capacity-componentadjust parts) 10-a, 10-b, and an even-number mode resonance-waveguide insuch a shape as to be formed when the stub 11 having a length 1 isconnected to an end face on the opposite side of the open-end of thestrip, wherein the first dual band resonator operates as the odd-numbermode resonance-waveguide, when the electric current flows to thesymmetric A-B planes of the stubs 11, while operating as the even-numbermode resonance-waveguide when the electric current does not flow to thesymmetric A-B planes. The second dual-band resonator is identical inconfiguration to the first dual-band resonator, and the orientationthereof is varied by 180 degrees, and provided with an H-shapedwaveguide 12, an end face thereof having a length n, and located at agiven interval m away from the first dual-band resonator, andincorporates the half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b. The third dual-bandresonator is identical in configuration to the first dual-bandresonator, and the orientation thereof is varied by 180 degrees, andprovided with an H-shaped waveguide 12, an end face thereof having alength n, and located at a given interval m away from the seconddual-band resonator. The second dual-band resonator is provided betweenthe first dual-band resonator and the third dual-band resonator, whereinfeeder conductor lines 13 are provided along the half-wavelengthresonator 10 of the first dual-band resonator as well as the thirddual-band resonator. The feeder conductor line 13 on one side functionsas an input side, while the feeder conductor line 13 on the other sidefunctions as an output side. The multistage-type dual-band band-passfilter further includes the fourth, the fifth, the . . . nth dual-bandresonators, and serves as the n-stage dual-band band-pass filter,characterized in that a dielectric rod 25 having a circular crosssection is provided in the space above each of the half-wavelengthresonator protrusions (capacity-component adjust parts) 10-a, 10-b ofthe half-wavelength resonator 10, and the dielectric rod 25 having acircular cross section is provided in the space above each of therespective stubs 11.

Further, the present invention provides a tunable dual-band resonatorstructured such that each stub 11 is added to each half-wavelengthresonator 10, and stepped impedance structures 10-a′, 10-b′ which arestructured or formed by extending half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b close to a connectionportion between each stub 11 and each half-wavelength resonator 10, andsymmetric A-B planes of the stubs 11 function as an electrical/magneticwall, respectively.

The dual-band resonator operates in two frequency-bands due to theresonance in an odd-number mode and resonance in an even-number mode,and can adjust the resonator length such that the half-wavelengthresonator 10 serves as the resonator in the odd-number mode, whereas thehalf-wavelength resonator 10 and the stub 11 serve as the resonator inthe even-number mode, thereby causing the odd-number mode to resonate ona low-frequency side, while causing the even-number mode to resonate ona high-frequency side, alternatively, enabling the odd-number mode toresonate on the high-frequency side, while enabling the even-number modeto resonate on the low-frequency side.

The dual-band resonator is made up of an odd-number mode resonator inthe shape including a ground conductor in a predetermined thicknessdisposed on the back surface of a dielectric body, and a strip conductordisposed on the top surface of the dielectric body, the relevant stripconductor is one length of a thin strip conductor cut off at an open-endthereof (the location where the strip is not linked), provided with adeeply retreated groove having a width g, and one length of the stripconductor is in a laterally symmetric shape, having a width d, andprovided at the tip of the groove as well as the end face of the stripconductor, and an even-number mode resonator in such a shape as to beformed when the stub 11 having a length 1 is connected to an end face onthe opposite side of the open-end of the strip, wherein the dual-bandresonator operates as the odd-number mode resonator, when the electriccurrent flows to the symmetric A-B planes of the stubs 11, whileoperates as the even-number mode resonator when the electric currentdoes not flow to the symmetric A-B planes, characterized in that adielectric rod 25 having a circular cross section is provided in thespace above the respective stubs 11, and another dielectric rod 25having a circular cross section is provided in the space above thestepped impedance structures 10-a′, 10-b′ of the half-wavelengthresonator 10, wherein each rod 25 is vertically moved in given positionsto implement tuning, thereby enabling a resonance frequency in theodd-number mode and a resonance frequency in the even-number mode to betuned independently from each other.

Further, the present invention provides a tunable dual-band band-passfilter having a structure incorporating a dual band resonator structuredsuch that each stub 11 is added to each half-wavelength resonator 10,and stepped impedance structures 10-a′, 10-b′ which are structured orformed by extending half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b close to a connection pointbetween each stub 11 and each half-wavelength resonator 10, andsymmetric A-B planes of the stubs 11 function as an electrical/magneticwall, respectively.

The dual-band resonator operates in two frequency-bands due to theresonance in an odd-number mode and resonance in an even-number mode,and can adjust the resonator length such that the half-wavelengthresonator 10 serves as the resonator in the odd-number mode, whereas thehalf-wavelength resonator 10 and the stub 11 serve as the resonator inthe even-number mode, thereby causing the odd-number mode to resonate ona low-frequency side, while causing the even-number mode to resonate ona high-frequency side, alternatively, enabling the odd-number mode toresonate on the high-frequency side, while enabling the even-number modeto resonate on the low-frequency side.

The dual-band resonator is made up of an odd-number mode resonator inthe shape including a ground conductor in a predetermined thicknessdisposed on the back surface of a dielectric body, and a strip conductordisposed on the top surface of the dielectric body, the relevant stripconductor is one length of a thin strip conductor cut off at an open-endthereof (the location where the strip is not linked), provided with adeeply retreated groove having a width g, and one length of the stripconductor is in a laterally symmetric shape, having a width d, andprovided at the tip of the groove as well as the end face of the stripconductor, and an even-number mode resonator in such a shape as to beformed when the stub 11 having a length 1 is connected to an end face onthe opposite side of the open-end of the strip, wherein the dual-bandresonator operates as the odd-number mode resonator, when the electriccurrent flows to the symmetric A-B planes of the stubs 11, whileoperating as the even-number mode resonator when the electric currentdoes not flow to the symmetric A-B planes, characterized in that adielectric rod 25 having a circular cross section is provided in thespace above the respective stubs 11, and another dielectric rod 25having a circular cross section is provided in the space above thestepped impedance structures 10-a′, 10-b′ of the half-wavelengthresonator 10, wherein each rod 25 is vertically moved in given positionsto implement tuning, thereby enabling the resonance frequency in theodd-number mode and the resonance frequency in the even-number mode tobe tuned independently from each other.

Still further, the present invention provides a tunable dual-bandresonator, according to the tunable dual-band resonator set forth above,wherein protrusions (capacity-component adjust parts) 10-a′1, 10-b′1 areprovided by expanding a part of the stepped impedance structures 10-a′,10-b′ in an outward direction of the groove, respectively.

More still further, the present invention provides a tunable dual-bandband-pass filter employing the tunable dual-band resonator set forthabove.

Further, the present invention provides a multistage-type (n-stage)dual-band band-pass filter having a structure incorporating thedual-band resonator set forth above, and each dual-band resonator havinga structure incorporating n-units (in total) of dual-band resonators(first, second, third, fourth, . . . nth resonators). The firstdual-band resonator has protrusions (capacity-component adjust parts)10-a′1, 10-b′1 which are provided by expanding a part of the steppedimpedance structures 10-a′, 10-b′ in an outward direction of the groove.The second dual-band resonator is identical in configuration to thefirst dual-band resonator, and the orientation thereof is varied by 180degrees, and provided with an H-shaped waveguide 12, an end face thereofhaving a length n, and located at a given interval m away from the firstdual-band resonator. The third dual-band resonator is identical inconfiguration to the first dual-band resonator, and the orientationthereof is varied by 180 degrees, and provided with an H-shapedwaveguide 12, an end face thereof having a length n, and located at agiven interval m away from the second dual-band resonator. The seconddual-band resonator is provided between the first dual-band resonatorand the third dual-band resonator, wherein feeder conductor lines 13 areprovided along half-wavelength resonator 10 of the first dual-bandresonator as well as the third dual-band resonator. The feeder conductorline 13 on one side functions as an input side, while the feederconductor line 13 on the other side functions as an output side. Themultistage-type dual-band band-pass filter further includes the fourth,the fifth, the . . . nth dual-band resonators, and serves as the n-stagedual-band band-pass filter, characterized in that a dielectric rod 25having a circular cross section is provided in the space above each ofthe protrusions (capacity-component adjust parts) 10-a′1, 10-b′1 thatare provided by expanding a part of the stepped impedance structures10-a′, 10-b′ in an outward direction of the groove, and anotherdielectric rod 25 having a circular cross section is provided in thespace above each of the respective stubs 11.

Advantageous Effects of Invention

The present invention has a high design-flexibility with respect to thecenter-frequency, the band-width, and input/output matching, in each ofthe two pass-bands. Further, with the present invention, the respectivecenter-frequencies of the two pass-bands can be tuned independently fromeach other, and furthermore, the band-pass characteristics, undergoingdegeneration after the tuning, can be improved. The present inventioncan provide both a tunable dual-band resonator, in which the shift widthof the resonance in the odd-number mode can be considerably increased,and a tunable dual-band band-pass filter using the tunable dual-bandresonator.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view showing a conventional dual band resonator;

FIG. 2 is a side view showing a dual band resonator according to thepresent invention;

FIG. 3 is a view showing a dielectric rod 25 that has an ellipse-likecross section and is highly efficient in varying a shift amount ofresonance in an odd-number mode proposed by the inventors of the presentinvention (reference example);

FIG. 4 is a plan view showing a dual band resonator used in the presentinvention;

FIG. 5(a) is a view showing electric-current distribution in thedual-band resonator adopted in the present invention in case ofodd-number mode, FIG. 5(b) is a view showing electric-currentdistribution in the dual-band resonator in case of even-number mode;

FIG. 6 is a view showing a half-wavelength resonator 10 provided withhalf-wavelength resonator protrusions (capacity-component adjust parts)10-a, 10-b (upper part in figure), and a half-wavelength resonator 10not provided with the half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b (lower part in figure);

FIG. 7(a) is a view showing the frequency characteristics of thehalf-wavelength resonator 10 provided with the half-wavelength resonatorprotrusions (capacity-component adjust parts) 10-a, 10-b (upper part infigure), and FIG. 7(b) is a view showing frequency characteristics ofthe half-wavelength resonator 10 not provided with half-wavelengthresonator protrusions (capacity-component adjust parts) 10-a, 10-b(lower part in figure);

FIG. 8 is a view showing a two-stage tunable dual-band band-pass filteradopting the half-wavelength resonator 10 provided with thehalf-wavelength resonator protrusions (capacity-component adjust parts)10-a, 10-b;

FIG. 9 is a view showing a three-stage tunable dual-band band-passfilter adopting the half-wavelength resonator 10 provided with thehalf-wavelength resonator protrusions (capacity-component adjust parts)10-a, 10-b;

FIG. 10 is a view showing a six-stage tunable dual-band band-pass filteradopting the half-wavelength resonator provided with the half-wavelengthresonator protrusions (capacity-component adjust parts) 10-a, 10-b(upper part in figure), and the frequency characteristics thereof (lowerpart in figure);

FIG. 11(a) is a view showing a common dual band resonator, and FIG.11(b) is a view showing a dual band resonator wherein a half-wavelengthresonator is structured in a stepped impedance structure;

FIG. 12(a) is a view showing frequency characteristics of the commondual-band resonator in both of the cases where a dielectric rod isprovided and the case where the dielectric rod is not provided, FIG.12(b) is a view showing frequency characteristics of the dual-bandresonator, wherein a half-wavelength resonator is structured in astepped impedance structure, in both of the cases where a dielectric rodis provided and the case where the dielectric rod is not provided;

FIG. 13 is a plan view of a dual band resonator, wherein ahalf-wavelength resonator is structured in a stepped impedance structureand provided with half-wavelength resonator protrusions(capacity-component adjust parts) 10-a′1, 10-b′1;

FIG. 14 is a view showing the frequency characteristics of the dual-bandresonator, wherein a half-wavelength resonator is structured in astepped impedance structure and provided with half-wavelength resonatorprotrusions (capacity-component adjust parts) 10-a′1, 10-b′1, in both ofthe cases where a dielectric rod is provided and the case where thedielectric rod is not provided;

FIG. 15 is a view showing a four-stage tunable dual-band band-passfilter having a structure incorporating the dual-band resonator, that isprovided with the stepped impedance structure and the half-wavelengthresonator protrusions (capacity-component adjust parts) 10-a′1, 10-b′1;and

FIG. 16 is a view showing the frequency characteristics of the dual-bandresonator, with respect to the four-stage tunable dual-band band-passfilter, provided with the stepped impedance structure and thehalf-wavelength resonator protrusions (capacity-component adjust parts)10-a′1, 10-b′1 in both of the cases where the dielectric rod 25 isprovided in the space above the half-wavelength resonator 10, and thecase where the dielectric rod 25 is not provided.

BEST MODE FOR CARRYING OUT THE INVENTION

For the dielectric substrate for use in the present invention, use canbe made of a commonly-known dielectric body, and a dielectric bodyhaving an excellent formability is preferably used. A material having asmall dielectric dissipation factor is preferable in order to controlthe dielectric loss. Further, a material having a high heat conductivityis preferable in order to control the rise in temperature. Further, withreference to a normal conductor as well as a superconductor, for use inthe strip conductor and a microstrip-line, respectively, use can be ofany known material. Still further, with reference to the constituentmaterial of each of the half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b, and the normal conductoras well as the superconductor, for use in the strip conductor and themicrostrip-line, respectively, as well, use can be of any knownmaterial.

In FIG. 4, there is shown a structure of the resonator for use in thepresent invention, as a representative constituent-unit. FIG. 4 is aview showing the half-wavelength resonator (resonance in the odd-numbermode) 10 provided with the half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b, the half-wavelengthresonator 10 being basically in the shape of a laterally symmetricmicrostrip-line structure resembling hairpins, each thereof beingprovided with the groove having a width g.

In FIG. 4, the stub 11 is shown at the right-side end. For a constituentmaterial of the stub 11, as well, use can be made of any known materialfor use in the normal conductor as well as the superconductor, used inthe strip conductor and the microstrip-line, respectively. As to theshape of each of the half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b, it need only be sufficientfor the half-wavelength resonator protrusion to protrude along the stripconductor, and the half-wavelength resonator protrusion may berectangular or staircase-like in shape, however, it is preferablylaterally symmetric in shape.

At the center of FIG. 4, with the dual-band resonator structured suchthat the stub 11 is added to each half-wavelength resonator 10 in theshape of a hairpin, symmetric A-B planes of the stubs 11 function as anelectrical/magnetic wall, respectively. The dual-band resonator operatesin two frequency-bands due to the resonance in an odd-number mode andresonance in an even-number mode, and it can adjust a resonator lengthsuch that the half-wavelength resonator 10 serves as the resonator inthe odd-number mode, whereas the half-wavelength resonator 10 and thestub serve 11 as the resonator in the even-number mode, thereby causingthe odd-number mode to resonate on a low-frequency side, while causingthe even-number mode to resonate on a high-frequency side, alternativelyenabling the odd-number mode to resonate on the high-frequency side,while enabling the even-number mode to resonate on the low-frequencyside. The dual-band resonator is made up of an odd-number mode resonatorincluding a ground conductor in a predetermined thickness disposed onthe back surface of a dielectric body, and a strip conductor disposed onthe top surface thereof, wherein the relevant strip conductor is onelength of a thin strip conductor cut off at an open-end thereof (thelocation where the strip is not linked), and provided with a deeplyretreated groove having a width g, and the one length of the stripconductor is in a laterally symmetric shape, and has a width d, that isprovided at the tip of the groove as well as the end face of the stripconductor. The dual-band resonator is also made up of an even-numbermode resonator in such a shape that the stub 11 having a length 1 isconnected to an end face on the opposite side of the open-end of thestrip, wherein the dual-band resonator is characterized in operating asthe odd-number mode resonator, when the electric current flows to thesymmetric A-B planes of the stubs 11, while operating as the even-numbermode resonator when the electric current does not flow to the symmetricA-B planes, as shown in FIG. 5.

The dual-band resonator can make up a dual-band band-pass filter singlyor by combination of plural units.

The respective constituent materials of the strip conductor 10(half-wavelength resonator), and the dielectric rod 25 which is movablein a direction vertical to the stub 11 are each preferably a materialhaving a high dielectric constant and low dielectric dissipation factor,the material including sapphire, Kyosera V380, and so forth. Thedielectric rod 25 according to the present invention is preferably in abar-like shape having a circular cross section to be structured so as tobe pushed in by turning a screw. Further, the diameter of a circle incross section is preferably in a range of the width g of the groove upto the outer width across the two lengths of the strip conductor 10(half-wavelength resonator), at the maximum.

Since the tunable dual-band resonator and the tunable dual-band ban-passfilter using the tunable dual-band resonator according to the presentinvention are basically the same as those disclosed in Patent Document 3(JP 2014-014962) because the present invention is different from PatentDocument 3 only in the point of use of the half-wavelength resonatorprovided with the half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b instead of thehalf-wavelength resonator, which was proposed by the inventors of thepresent invention, and hence the basic structures of the tunabledual-band resonator and the tunable dual-band ban-pass filter using thetunable dual-band resonator according to the present invention are thesame as those of the tunable dual-band resonator and the tunabledual-band ban-pass filter using the tunable dual-band resonator, whichwere disclosed in Patent Document 3 and proposed by the inventors of thepresent invention. Accordingly, with the tunable dual-band ban-passfilter according to the present invention, it is possible to implementthe adjustment method of the shift amount of frequency-tuning foradjusting the band-pass characteristics in the odd-number mode alone,the adjustment method of the shift amount of frequency-tuning foradjusting the band-pass characteristics in the even-number mode alone,and the method of improving or trimming the degeneration in theband-pass characteristics, occurring after the tuning of thefrequencies, in the same way as disclosed in Patent Document 3.

Although a structure of the present invention is described next, it ispossible for those skilled in the art to imitate and manufacture adual-band ban-pass filter resembling the structure of the presentinvention, and hence the present invention is not limited only to thestructure as described hereunder.

Example 1

For an embodiment of the resonator according to the present invention,use is made of a microstrip-line structure, however, it is to be pointedout that the present invention is not limited thereto.

With the present invention, the microstrip-line structure was adopted,and the external appearance of the resonator as a whole is as shown inFIG. 2. More specifically, a strip conductor 23 (equivalent to ahalf-wavelength resonator 10, a stub 11, a waveguide 12, and a feederconductor line 13, etc.) is provided on the top of a dielectric body 22and a ground conductor 21 is provided underneath the dielectric body 22.The dielectric body 22 is preferably formed by use of a material havinga small dielectric dissipation factor in order to control the dielectricloss. Further, the dielectric body 22 is preferably formed by the use ofa material having a high heat conductivity in order to control the risein temperature. The ground conductor 21 is preferably formed by the useof a material having a small conductor loss, a superconducting material,in particular. The strip conductor as well is preferably formed by theuse of a material having a small conductor loss, a superconductingmaterial, in particular (the foregoing can be said of all figuresshowing the resonator as well as the filter, using the microstrip-linestructure). A switch can be provided as necessary between thehalf-wavelength resonator 10 and the stud 11, in FIG. 4, however, thepresent embodiment shows one without the switch being provided.

In the dual-band resonator of FIG. 4, the A-B plane functions as theelectrical/magnetic wall, and the dual-band resonator serves as thedual-band band-pass filter operating in the two frequency-bands due tothe resonance in the odd-number mode and resonance in the even-numbermode. The dual-band resonator is of a basic structure in which the stub11 is added to the half-wavelength resonators 10. Further, the dual-bandresonator serves as the resonator in the odd-number mode, whereas thehalf-wavelength resonator, together with the stub, serves as theresonator in the even-number mode.

FIG. 5 is a view showing the electric-current distribution in thedual-band resonator according to the present invention. In the case ofthe odd-number mode, an electric-current flowing through the dual-bandresonator will flow through only the half-wavelength resonator 10,whereupon the half-wavelength resonator 10 operates as an odd-numbermode resonator as shown in FIG. 5(a). A bend part of the half-wavelengthresonator 10 is the central part thereof at this point in time, having avoltage at 0 and the electric-current at the maximum, so that the bendpart can be regarded as GND, the stub 11 therefore exerting no influenceon the resonance frequency of the half-wavelength resonator 10. In thecase of the even-number mode, the electric-current flows through boththe half-wavelength resonator 10 and the stub 11, whereupon thehalf-wavelength resonator 10 operates as a half-wavelength straight-lineresonator as shown in FIG. 5(b).

As is evident from the electric-current distribution set forth above,the half-wavelength resonator 10 can function as the odd-number moderesonator when the current flows through the symmetric A-B planes, whilethe half-wavelength resonator 10 can function as the even-number moderesonator when the current does not flow through the symmetric A-Bplanes, so that the half-wavelength resonator 10 functions as thedual-band resonator.

According to the resonator of the present invention, the resonatorlength was adjusted so that the odd-number mode resonates on alow-frequency side, while the even-number mode resonates on ahigh-frequency side. In some cases, the resonator length can be adjustedso that the odd-number mode resonates on the high-frequency side, whilethe even-number mode resonates on the low-frequency side. It is desiredto downsize the dual-band resonator by assembling the half-wavelengthresonator 10 and stub 11 into a stepped impedance structure.

A figure shown in the upper part of FIG. 6 is a sectional view of anexample of a tunable dual-band resonator configured according to thepresent invention. The half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b are manufactured integrallywith the half-wavelength resonator 10 composed of microstrip conductorsmaking up the resonator. Further, a feeder conductor line 13 is providedalong the half-wavelength resonator 10 for the purpose of inputting asignal to/outputting a signal from the dual-band resonator.

It was possible to considerably increase the shifting width in theodd-number mode by providing the dielectric rod 25 in the space aboveeach of the half-wavelength resonator protrusions (capacity-componentadjust parts) 10-a, 10-b of the half-wavelength resonator 10, and movingthe dielectric rod 25 in a direction perpendicular to the planes of thestrip conductor (half-wavelength resonator) 10 (see FIG. 7(a)). At thispoint in time, since the resonance frequency of the dual-band resonatorin the odd-number mode alone is shifted while that in the even-numbermode shows a fixed value, it is possible to completely tune theresonance frequency in the even-number mode and resonance frequency inthe odd-number mode, independently from each other.

Comparative Example

A figure shown in the lower part of FIG. 6 is a sectional view of atunable dual-band resonator configured for the purpose of comparison.This is the half-wavelength resonator 10, composed of microstripconductors making up the resonator not provided with the half-wavelengthresonator protrusions (capacity-component adjust parts) 10-a, 10-b.Further, a feeder conductor line 13 is provided along thehalf-wavelength resonator 10 for the purpose of inputting a signalto/outputting a signal from the dual-band resonator. A feeder conductorline 13 is provided along the other half-wavelength resonator 10 inorder to take out a signal.

With respect to this resonator, that is a tunable dual-band resonatorcharacterized in that the dielectric rod 25 having a circular crosssection is provided in the space above a common half-wavelengthresonator 10 not provided with the half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b, frequency characteristicsof the resonator was examined in both of the cases where the dielectricrod 25 having a circular cross section is provided in the space abovethe half-wavelength resonator 10, so as to oppose the plane of the stripconductor 23, and the case where the dielectric rod 25 having a circularcross section is not provided.

In order to check the examination results, a simulation was conducted byuse of a three-dimensional electromagnetic-field analytical simulator(manufactured by AET Corp.). The resonance frequency of the dual-bandresonator was 2.25 GHz in the odd-number mode, and 3.5 GHz in theeven-number mode. The dielectric constant of the dielectric rod 25 was39, and the diameter of the dielectric rod 25 was the same as the widthof the dual-band resonator. In this case, the diameter of the dielectricrod 25 was 2.5 mm. Further, the dielectric rod 25 was 20 mm in length. Adistance between the dual-band resonator and the dielectric rod 25 was0.01 mm when the dielectric rod 25 was disposed.

It is evident from the FIG. 7(a) that a shift width in the odd-numbermode of the half-wavelength resonator 10 provided with thehalf-wavelength resonator protrusions (capacity-component adjust parts)10-a, 10-b is increased about 1.8 times as much as that in the case ofthe common half-wavelength resonator 10 (FIG. 7(b)) not provided withthe half-wavelength resonator protrusions (capacity-component adjustparts) 10-a, 10-b. Since the frequency in the even-number mode is notshifted in this case, it is evident that the resonance frequency only inthe odd-number mode can be independently adjusted.

Example 2

FIG. 8 shows a tunable dual-band band-pass filter made up by combiningthe tunable dual-band resistor of the present invention in two stages.Depicted by 12 is a waveguide, and in order to input a signal to/outputa signal from the tunable dual-band band-pass filter, a feeder conductorline 13 is disposed along a half-wavelength resonator 10 on theleft-hand side. In order to take out a signal, a feeder conductor line13 is disposed along a half-wavelength resonator 10 on the right-handside. Although a dielectric rod 25 is provided in the space above eachof the half-wavelength resonator protrusions (capacity-component adjustparts) 10-a, 10-b, and a dielectric rod 25 is provided in the spaceabove each of the respective stubs 11, they are not shown in FIG. 8.

Example 3

FIG. 9 shows a tunable dual-band band-pass filter made up by combiningthe tunable dual-band resistor of the present invention in three stages.Depicted by 12 is a waveguide, and in order to input a signal to/outputa signal from the tunable dual-band band-pass filter, a feeder conductorline 13 is disposed along a half-wavelength resonator 10 on theleft-hand side. In order to take out a signal, a feeder conductor line13 is disposed along a half-wavelength resonator 10 on the right-handside. A dielectric rod 25 provided in the space above each of thehalf-wavelength resonator protrusions (capacity-component adjust parts)10-a, 10-b, and a dielectric rod 25 provided in the space above each ofthe respective stubs 11 are not shown in FIG. 9.

Example 4

FIG. 10 is a plan view showing one example or embodiment of a six-stagedual-band band-pass filter according to the present invention, using amicrostrip-line structure. Depicted by 12 is a waveguide, and in orderto input a signal to/output a signal from a tunable dual-band band-passfilter, a feeder conductor line 13 is disposed along a half-wavelengthresonator 10 on the left-hand side. In order to take out a signal, afeeder conductor line 13 is disposed along a half-wavelength resonator10 on the right-hand side. A dielectric rod 25 provided in the spaceabove each of the half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b of the half-wavelengthresonator 10 and a dielectric rod 25 provided in the space above each ofthe respective stubs 11 are not depicted in FIG. 10.

Further, in a figure in the lower part of FIG. 10, there are shown thecharacteristics of the six-stage dual-band band-pass filter, in the casewhere the dielectric rod 25 is inserted in the half-wavelength resonator10, and in the case where the dielectric rod 25 is not inserted in thehalf-wavelength resonator 10, respectively. It has been confirmed thatwith the dual-band band-pass filter using the half- wavelength resonator10 provided with the half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b, according to the presentinvention, the center-frequency in the odd-number mode is foundconsiderably shifted.

Example 5

FIG. 11(b) is a plan view showing one example of a dual band resonatorconstituted according to the present invention. Since a half-wavelengthresonator 10 is structured in a stepped impedance structure, the shiftamount of resonance frequency in the odd-number mode is increased.According to the stepped impedance structure of the half-wavelengthresonator 10 as shown in FIG. 11(b), the line width is thinned at theportion close to the open end and thickened up to a portion close to aconnection portion between each stub 11 and each half-wavelengthresonator 10, thereby causing the half-wavelength resonator protrusions(capacity-component adjust parts) 10-a, 10-b to be structured in thestepped impedance structures 10-a′, 10-b′ by extending thehalf-wavelength resonator protrusions close to the connection portionbetween the stub 11 and the half-wavelength resonator 10. With such aconfiguration, the entire length of the half-wavelength resonator 10 asshown in FIG. 11(b) becomes longer compared with the half-wavelengthresonator 10 of the common dual band resonator having no steppedimpedance structures 10-a′, 10-b′ shown in FIG. 11(a).

With respect to this resonator, that is a tunable dual-band resonatorcharacterized in that the dielectric rod 25 having a circular crosssection is provided in the space above a common half-wavelengthresonator 10, the frequency characteristics of the resonator wasexamined in both the cases where the dielectric rod 25 having a circularcross section is provided in the space above the half-wavelengthresonator 10, so as to oppose the plane of the strip conductor 23, andthe case where the dielectric rod 25 having a circular cross section isnot provided.

In order to check the examination results, a simulation was conducted byuse of a three-dimensional electromagnetic-field analytical simulator(manufactured by AET Corp.). The resonance frequency of the dual-bandresonator was 1.5 GHz in the odd-number mode and 2.0 GHz in theeven-number mode. The dielectric constant of the dielectric rod 25 was39 and the diameter of the dielectric rod 25 was the same as the widthof the dual-band resonator. In this case, the diameter of the dielectricrod 25 was 2.0 mm. Further, the dielectric rod 25 was 20 mm in length.The distance between the dual-band resonator and the dielectric rod 25was 0.01 mm when the dielectric rod 25 was disposed.

It is evident from the FIG. 12(b) that a shift width in the odd-numbermode of the half-wavelength resonator 10 provided with the steppedimpedance structures 10-a′, 10-b′ is increased about 2.3 times as muchas that in the case of the common half-wavelength resonator 10 (FIG.12(a)) not provided with the stepped impedance structures 10-a′, 10-b′.Since the frequency in the even-number mode is not shifted in this case,it is evident that the resonance frequency only in the odd-number modecan be independently adjusted.

With respect to the configuration of the resonator shown in FIG. 11(b),in order to increase the shift amount of the resonance frequency in theodd-mode tuning, protrusions (capacity-component adjust parts) 10-a′1,10-b′1 are added. With such an addition of the protrusions, it ispossible to use a dielectric rod having a larger diameter than thedielectric rod used in FIG. 11(b), the variation amount of the capacitycomponent of the resonator is increased, so that the shift amount of theresonance frequency in the odd-mode is increased.

In FIG. 14, there is shown the frequency characteristics of theresonator in both the cases where the dielectric rod 25 having acircular cross section is provided and the case dielectric rod 25 havinga circular cross section is not provided. The diameter of the dielectricrod 25 used in this case was 2.5 mm and is made larger than thedielectric rod 25 by 0.5 mm. From FIG. 14, since the shift amount of theresonance frequency was about 163 MHz, the shift amount of the resonancefrequency was increased about 3.26 times as much as that in the case ofusing the common half-wavelength resonator 10 shown in FIG. 11(a). Sincethe frequency in the even-number mode is not shifted in this case, it isevident that the resonance frequency only in the odd-number mode can beindependently adjusted.

Example 6

FIG. 15 is a plan view showing an example of a four-stage tunabledual-band band-pass filter having a structure incorporating thedual-band resonator configured by the present invention, each dual-bandresonator is provided with the stepped impedance structure and thehalf-wavelength resonator protrusions (capacity-component adjust parts)10-a′1, 10-b′1, and employs a microstrip-line structure. Depicted by 12is a waveguide, and in order to input a signal to/output a signal from atunable dual-band band-pass filter, a feeder conductor line 13 isdisposed along a half-wavelength resonator 10 on the left-hand side. Inorder to take out a signal, a feeder conductor line 13 is disposed alonga half-wavelength resonator 10 on the right-hand side. There is notshown the dielectric rod 25 provided in the space above thehalf-wavelength resonator protrusions (capacity-component adjust parts)10-a′1, 10-b′1 and another dielectric rod 25 provided in the space abovethe respective stubs 11.

Further, with respect to the four-stage tunable dual-band band-passfilter, FIG. 16 shows the frequency characteristics of the resonator inboth the cases where the dielectric rod 25 was inserted in the spaceabove the half-wavelength resonator 10, and the case where thedielectric rod 25 was not inserted.

It has been confirmed that with the dual-band band-pass filter using thehalf-wavelength resonator 10 provided with the stepped impedancestructures and the half-wavelength resonator protrusions(capacity-component adjust parts) 10-a′1, 10-b′1, according to thepresent invention, the center-frequency in the odd-number mode is foundconsiderably shifted.

INDUSTRIAL UTILIZATION

Since the tunable dual-band resonator and the tunable dual-bandband-pass filter using the tunable dual-band resonator can adjust thecenter-frequencies of each band independently from each other, and canconsiderably shift the center frequencies in each odd-number mode, andalso can improve the band-pass characteristics, undergoing degenerationafter the tuning of the respective center-frequencies, the presentinvention can be diverted to all sorts of filters used forcommunication, to thereby contribute to the development of thecommunications fields and result in extremely-high industrialutilization.

1-17. (canceled)
 18. A tunable dual-band resonator operating in twofrequency-bands due to resonance in an odd-mode and resonance in aneven-mode, the tunable dual-band resonator comprising: a groundconductor; a dielectric body situated over the ground conductor; and astrip conductor situated over the dielectric body, the strip conductorcomprising: a half-wavelength resonator having a pair of portions whichare arranged oppositely; and a stub coupled with the half-wavelengthresonator, wherein the ground conductor, the dielectric body and thestrip conductor form a micro strip-line structure, each of the pair ofportions of the half-wavelength resonator has a protrusion, a dielectricrod is provided above the protrusion of each of the pair of portions ofthe half-wavelength resonator and the dielectric rod is verticallymovable to tune a resonance frequency in the odd-mode and anotherresonance frequency in the even-mode independently.
 19. The tunabledual-band resonator according to claim 18, wherein the pair of portionsof the half-wavelength resonator have a symmetric structure in a planview.
 20. The tunable dual-band resonator according to claim 19, whereinthe pair of portions of the half-wavelength resonator are parallel toeach other.
 21. The tunable dual-band resonator according to claim 18,wherein the strip conductor is comprised of a superconducting material.22. The tunable dual-band resonator according to claim 18, wherein theprotrusion is used for adjusting capacitance of the half-wavelengthresonator.
 23. The tunable dual-band resonator according to claim 18,wherein the protrusion has a rectangular shape in a plan view.
 24. Thetunable dual-band resonator according to claim 18, wherein theprotrusion has a stepwise shape in a plan view.
 25. The tunabledual-band resonator according to claim 18, wherein each of the pair ofportions of the half-wavelength resonator has an end portion and anotherend portion, the stub is connected to the end portion of each of thepair of portions of the half-wavelength resonator and the protrusion ispositioned between the end portion and said another end portion.
 26. Thetunable dual-band resonator according to claim 18, wherein thedielectric rod is circular in cross section.
 27. The tunable dual-bandresonator according to claim 18, wherein the dielectric rod is comprisedof sapphire.
 28. The tunable dual-band resonator according to claim 18,wherein the dielectric rod is structured so as to be pushed in byturning a screw.
 29. The tunable dual-band resonator according to claim18, wherein each of the pair of portions of the half-wavelengthresonator has a length for serving as a resonator in an odd-mode. 30.The tunable dual-band resonator according to claim 18, wherein surfacesof the pair of portions of the half-wavelength resonator arrangedoppositely function as an electrical/magnetic walls.
 31. The tunabledual-band resonator according to claim 18, wherein the half-wavelengthresonator serves as the resonator in the odd-mode and thehalf-wavelength resonator and the stub serve as the resonator in theeven-mode.